1. Field of the Invention
The present invention relates to a video signal coding apparatus for coding a video signal.
2. Description of the Related Art
In recent years, techniques for compressing digital video signals have been developed. A huge amount of funds and labor, however, are required to standardize a compression method and to implement a compression algorithm in hardware (LSI), so attempts are being made to make minor changes in a compression algorithm that has been implemented in hardware using existing standards and commercially available video equipment in order to develop a new video signal coding apparatus.
FIG. 5 describes a conventional video signal coding apparatus that codes a 4:2:2 sampling signal using equipment for coding 4:1:1 sampling. The equipment for coding 4:1:1 sampling corresponds to a compression algorithm that has been implemented in hardware using existing standards and commercially available video equipment.
In FIG. 5, 501 is a video signal input terminal that inputs a digital video signal, 502 is an effective-area blocking. device for dividing only the effective area of the input signal into blocks and outputting the blocks to two channels, and 503 and 504 are effective-area encoders that hight-efficiency-codes the blocks in the effective area that have been input. The effective area is simply described. If the digital video signal is transmitted based on, for example, a 525/60 system, all the areas of the video signals within the transmitted signal is composed of 480 main lines and 3 or 7.5 accompanying lines. Herein, the 480 lines are referred to as an effective area and the accompanying lines are referred to as an additional area. Conventional video signal coding apparatuses process only the video signals in the effective area. If the digital video signal is transmitted based on, for example, a 625/50 system, all the areas of the video signals within the transmitted signal is composed of 576 main lines and 9 accompanying lines.
The operation of the conventional video signal encoder of this configuration is described.
A digital video signal with 4:2:2 sampling is input from the input terminal 501. The effective-area blocking device 502 divides only the effective area within the input signal into macro blocks.
During 4:1:1 signal sampling, the macro blocks are composed of four DCT (Discrete Cosine Transform) blocks for a luminance signal that are arranged continuously on a screen in the horizontal direction, and two DCT blocks for color difference signals that are arranged at the same positions of the screen as the four DCT blocks for a luminance signal. During 4:2:2 signal sampling, the macro blocks are composed of two DCT blocks for a luminance signal that are arranged continuously on the screen in the horizontal direction, and two DCT blocks for color difference signals that are arranged at the same positions of the screen as the two DCT blocks for a luminance signal.
Thus, since the number of macro-blocks per frame in a 4:2:2 signal is double that in a 4:1:1 signal, an effective-area encoder that can deal with 4:1:1 signals is adapted for two channels as shown in FIG. 5.
As described above, however, the number of DCT blocks within a single micro block is different between a 4:1:1 signal and a 4:2:2 signal, so the effective-area encoders 503 and 504 for 4:1:1 signals cannot be directly used. Thus, the effective-area blocking device 502 adds to the 4:2:2 signal, two DCT blocks consisting of dummy data so that the number of DCT blocks in a single macro block in the 4:2:2 signal is the same as that in the 4:1:1 signal, thereby enabling the use of the effective-area encoders 503 and 504 for 4:1:1 signals.
Thus, the effective-area blocking device 502 divides one-frame data into macro blocks including dummy DCT blocks in which all pixel values are the same, further divides the macro blocks for a single frame into two channels, and output the macro blocks to the effective-area encoders 503 and 504. As in the input of the 4:1:1 signal, the effective-area encoders 503 and 504 code the output from the effective-area blocking device 502. FIG. 6 shows a list of data obtained by applying the same coding to the macro blocks of the 4:2:2 signal as in the 4:1:1 signal.
As shown in FIG. 6, coding the 4:2:2 signal essentially uses an area to which are input AC components stored in four areas(e.i. areas 0, 2, 4, and 5) out of the six areas 0 to 5 to which data obtained by coding the 4:1:1 signal is input, and an area to which are input AC components stored in the areas 1 and 3 in which the dummy DCT blocks are recorded.
Since, however, the dummy DCT blocks whose all the data in the DCT blocks has the same pixel value, coding with the DCT blocks provides only DC values and no AC components. Consequently, data obtained by applying VLC (Variable Length Coding) to DCT data consists of only DC components and an EOB that is a coding end code. Thus, in FIG. 6, although 9 DC bits, 3 additional-information bits, and 4 AC bits are normally input to reserved areas 601 and 602, 9 DC bits from the dummy DCT blocks, 3 additional-information bits, and 4 coding end code (EOB) bits are input to these areas if the 4:2:2 signal is dealt with.
The area in which the AC components in the areas 1 and 2 are to be housed is used to record therein AC component data that cannot be stored in the other areas.
According to the above method, however, DC values and additional information for the dummy DCT blocks generated during the coding of the 4:2:2 signal are not required to decode a video signal from coded data, so the coded data includes useless data and cannot be efficiently used.
In view of this conventional problem, this invention provides a video signal coding apparatus that can use coded data more efficiently and that can improve the error immunity.
A first invention of the present invention is a video signal coding apparatus which comprises:
division means for dividing an input digital video signal into a first and a second areas;
first blocking means for dividing said first area into the units of first blocks;
first compression means for hight-efficiency-coding said first block to create a first compressed block;
second compression means for hight-efficiency-coding said second area to create second compressed data;
second blocking means for dividing said second compressed data into the units of second compressed blocks each including a luminance signal for a plurality of pixels and at least one color difference signal for pixels arranged at the same position as the plurality of pixels on a screen; and
substitution means for substituting said second compressed block for data stored in the same first compressed block at a predetermined position.
This configuration, for example, allows all coded data to be used effectively and inputs to the same block, luminance and color difference signals for a plurality of pixels located at the same position on a screen. Consequently, even if an error occurs, it affects only the plurality of the pixels compared to more pixels in the prior art, thereby substantially improving the error immunity to reduce the adverse effects on image quality during decoding.
A second invention of the present invention is a video signal coding apparatus which comprises:
division means for dividing an input digital video signal into a first and a second areas;
first blocking means for dividing said first area into a plurality of first blocks and dividing the plurality of said first blocks into x (xxe2x89xa72) channels for output;
first compression means for hight-efficiency-coding said first block to create a first compressed block;
second compression means for hight-efficiency-coding said second area to create second compressed data;
second blocking means for dividing said second compressed data into the units of second compressed blocks including a luminance signal for a plurality of pixels and at least one color difference signal for pixels arranged at the same position as the plurality of pixels on a screen and dividing said plurality of second compressed blocks into said x channels for output; and
substitution means operative in each of the x channels for substituting said second compressed block for data stored in the same first compressed block at a predetermined position.
This configuration, for example, enables the same effects as in the first invention to be achieved using a multichannel configuration.
A third invention of the present invention is a video signal coding apparatus which comprises:
division means for dividing an input digital video signal having a 4:2:2 sampling, into a first and a second areas;
first blocking means for dividing said first area into the units of first blocks;
first compression means for hight-efficiency-coding said first block to create a first compressed block;
second compression means for hight-efficiency-coding said second area to create additional compressed data;
second blocking means for dividing said second compressed data into the units of second compressed blocks each including two pixels for a luminance signal and two pixels for color difference signals arranged at the same position as said two pixels on a screen; and
substitution means for substituting said second compressed block for data stored in the same said first compressed block at a predetermined position.
This configuration, for example, inputs to the same block, luminance and color difference signals for two pixels located at the same position on a screen. Consequently, even if an error occurs, it affects only the two pixels compared to more pixels in the prior art, thereby substantially improving the error immunity to reduce the adverse effects on image quality during decoding.
A fourth invention of the present invention is a video signal coding apparatus which comprises:
division means for dividing an input digital video signal having a 4:2:2 sampling, into a first and a second areas;
first blocking means for dividing said first area into the units of first blocks;
first compression means for hight-efficiency-coding said first block to create a first compressed block;
second compression means for hight-efficiency-coding said second area to create second compressed data in which each data has 6 bits;
second blocking means for dividing said second compressed data into the units of second blocks each including two pixels for a luminance signal and two pixels for color difference signals arranged at the same position as said two pixels on a screen; and
substitution means for substituting the 12 bits of the two pixels for the luminance signal in said second compressed block, for data stored in the same said first compressed block in a predetermined area while substituting the 12 bits of the two pixels for the color difference signals in said second compressed block, for data stored in the same said first compressed block in another area.
This configuration, for example, provides the same effects as the third invention and the image for the added area is originally obtained by compressing 8-bit data into 6 bits, thereby enabling high image quality to be maintained despite decoding.
A fifth invention of the present invention is a video signal coding apparatus comprising: division means for dividing an input digital video signal into a first and a second areas; first blocking means for dividing said first area into the units of first blocks; first compression means for hight-efficiency-coding said first block to create a first compressed block; second blocking means for dividing said second area into the units of second blocks each including a luminance signal for a plurality of pixels and at least one color difference signal for pixels arranged at the same position as the plurality of pixels on a screen; second compression means for hight-efficiency-coding said second block to create second compressed data to output the data as a second compressed block; and substitution means for substituting said output second compressed block for data stored in the same said first compressed block at a predetermined position.
A sixth invention of the present invention is a video signal coding apparatus comprising: division means for dividing an input digital video signal into a first and a second areas; first blocking means for dividing said first area into the units of first blocks; first coding means for coding said first block to create a first coded block; second coding means for coding said second area to create second coded data; second blocking means for dividing said second coded data into the units of second coded blocks each including a luminance signal for a plurality of pixels and at least one color difference signal for pixels arranged at the same position as the plurality of pixels on a screen; and substitution means for substituting said second coded block for data stored in the same said first coded block at a predetermined position.
A seventh invention of the present invention is a video signal coding apparatus comprising: division means for dividing an input digital video signal into a first and a second areas; first blocking means for dividing said first area into the units of first blocks; first compression means for coding said first block into a first coded block; second blocking means for dividing said second area into the units of second coded blocks each including a luminance signal for a plurality of pixels and at least one color difference signal for pixels arranged at the same position as the plurality of pixels on a screen; second compression means for coding said second block to create a second coded data and output it as a second coded block; and substitution means for substituting said second coded block for data stored in the same said first coded block at a predetermined position.
The eighth invention of the present invention is a video signal coding apparatus according to any one of said first to seventh inventions wherein if said input digital video signal is transmitted based on a (1) 525/60 system, said first area has 480 lines while said second area has 7.5 lines, and wherein if said input digital video signal is transmitted based on a (2) 625/50 system, said first area has 576 lines while said second area has 9 lines.
The ninth invention of the present invention is a video signal coding apparatus according to any one of said first to fifth inventions wherein the hight-efficiency-coding executed by said first compression means involves transformation coding and wherein the hight-efficiency-coding executed by said second compression means is non-linear quantization.